JPH0148839B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for treating sludge. Biological methods such as the activated sludge method are widely used to treat organic wastewater such as sewage, human waste, pulp wastewater, and bean paste wastewater. In particular, the settling and dewatering properties of sludge are problematic. In other words, a decrease in the specific gravity of sludge due to proliferation of filamentous bacteria or swelling of bacterial cells forming flocs due to bound water causes a bulking phenomenon, resulting in the inability to concentrate sludge and the outflow of sludge from the surface layer of the settling tank. This will lead to further problems. Furthermore, the higher the water content of sludge, the more difficult it becomes to dehydrate the sludge and furthermore to incinerate the sludge. Various methods have been proposed to solve this problem, but a relatively preferable method is the use of acrylic acid hydrazide polymer compounds for dewatering sludge (Japanese Patent Laid-Open No. 58-36697). Public bulletin). However, even with this method, the sludge flocs are still fine and the gravitational resistance is insufficient. Another drawback is that the moisture content of the dehydrated cake is high. Even if heavy metal ions such as iron and manganese are used in combination with the polymer compound, the above drawbacks cannot be sufficiently overcome. An object of the present invention is to provide a method for treating sludge in which the gravitational separation of sludge is improved and the releasability from cloth and the moisture content of the treated cake are improved. That is, the sludge treatment method of the present invention includes adding an acrylic acid hydrazide-based polymer compound and a polymer compound containing an amino group or a quaternary ammonium salt to organic sludge, and further adding an acid or an acidic salt, a neutral salt, and This method is characterized by adding a solution containing at least one selected from alkali and alkaline salts. The acrylic acid hydrazide polymer compound (hereinafter referred to as AH polymer) used in the present invention has the general formula (In the formula, R represents H or CH ₃ , A represents a monomer unit of acrylamide, methacrylamide, acrylic ester, methacrylic ester, and B represents acrylic acid or a salt thereof, methacrylic acid or a salt thereof, or the above-mentioned A It represents a monomer unit copolymerizable with , and l, m and n have the following relationship: 0 mol%<l≦100 mol% n+m+l=100 mol%) is preferred. Examples of the B unit copolymerizable with the A unit include vinyl chloride, vinyl acetate, butadiene, styrene, acrylonitrile, and the like. The polymerization form of the AH polymer may be block type, alternating type, or random type. Further, the intrinsic viscosity of the AH polymer is preferably [η] 30° C. 1N-NaNO ₃ >0.1 (dl/g). An example of producing the AH polymer is shown below, but the method for producing the AH polymer is disclosed in detail in JP-A-55-144004. Examples of the polymer compound containing an amino group or a quaternary ammonium salt (hereinafter referred to as AA polymer) used in the present invention include aminoalkyl acrylates such as dimethylaminoethyl acrylate;
Examples include aminoalkyl methacrylates such as dimethylaminoethyl methacrylate, aminoalkyl acrylamides such as dimethylaminopropylacrylamide, aminoalkyl methacrylamides such as dimethylaminopropyl methacramide, and quaternized products thereof. In addition, copolymers with other monomers that can be copolymerized with these can also be used, and examples of other monomers include acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, vinyl acetate, acrylic ester, and methacrylic ester. etc. The intrinsic viscosity of the AA polymer is [η] 30°C 0.1N-NaCl desirably 5 dl/g or more. The processing effect can be improved by a solution containing the above-mentioned AH polymer and AA polymer. However, when the above polymers are made into a single liquid, the AH polymer often undergoes hydrolysis and acrylic acid or methacrylic acid is produced, and when the amount of these produced increases, a reaction occurs between the AH polymer and the AA polymer, which inevitably causes Even sushi does not have sufficient effect.
Therefore, in the present invention, an acid or an acidic salt or an alkali or an alkaline salt is present in the polymer-containing liquid to adjust the pH to 3 or less or 9 or more.
This prevents the reaction between AH polymer and AA polymer. As acids or acidic salts, HCl,
Examples include H ₂ SO ₄ , sulfamic acid, NaHSO _{4 ,} etc., and examples of alkali or alkaline salts include NaOH,
Examples include KOH, NH ₄ OH, Na ₂ CO ₃ and the like. other
The effect can be similarly improved by using alkaline earth metal ions which are neutral salts such as CaCl ₂ , MgCl ₂ and BaCl ₂ . In this case, it is not necessary to limit the pH range to the above. Although the object of the present invention is achieved by using a solution made of the above-mentioned materials, a metal salt can be added before adding this solution. As the metal salt, aluminum or iron salts are preferred, and aluminum salts are particularly preferred from the viewpoint of handling. Examples of aluminum salts include aluminum chloride, polyaluminum chloride (PAC), aluminum sulfate, etc., and iron salts include ferrous chloride, ferric chloride,
Examples include ferrous sulfate, ferric sulfate, polyferrous sulfate, and the like. The addition of these metal salts makes the sludge flocs more likely to settle. The content ratio of AH polymer and AA polymer in the solution added to sludge is 1:9 to 9: by weight.
1, preferably 2:8 to 8:2. The amount of this solution added is preferably 0.3 to 5.0% based on the SS of the sludge based on the polymer in the solution. When using metal salts, the amount of metal salts added should be 1 to 100% of the SS of sludge.
50%, preferably 3-30%. To carry out the method of the present invention, the above-mentioned poly and acid or alkali may be added to sludge in the same solution, stirred as appropriate to uniformly disperse the polymer in the sludge, and then dehydrated. Dewatering is carried out by known means such as a belt press, centrifuge, screw press, filter press, etc. According to the present invention, AH in the presence of acid or alkali
By combining polymer and AA polymer, AH
Larger and denser sludge flocs can be formed compared to when a polymer is used alone. Therefore, the sludge has excellent gravity separation properties, has a low water content in the dehydrated cake, and is easily peeled from cloth. Therefore, by carrying out the present invention, it is possible to improve the amount of sludge dewatered, and the present invention can be effectively used in wastewater treatment equipment that generates a large amount of sludge. Next, the effects of the present invention will be specifically explained using manufacturing examples and examples. The Preparation Example is an example of the preparation of the AH polymer used in the Examples. Polymethyl acrylate in the 4-necked flask of Production Example 3
Add 200g and 2kg of hydrazine hydrate aqueous solution,
The reaction was carried out at 80° C. for 5 hours while stirring. The resulting viscous solution was poured into about 20 methanol to obtain a white precipitate. This was taken, purified by reprecipitation, and dried under reduced pressure at 60°C to obtain an acrylic acid hydrazide polymer compound (hereinafter referred to as A). Examples 1 to 3, Comparative Examples 1 to 2 A sludge dewatering test was conducted using a solution containing the above A, a specific polymer, and an acid or alkali (with metal salts added in advance if necessary). The physical properties of these polymers are shown in Table 1.

【table】

[Table] The treated sludge and dewatering test methods are as follows. <Sludge> Mixed sludge of sewage (initial settling sludge and surplus sludge) PH6.0, SS = 2.16%, VSS/SS = 78.6% <Dehydration test method> (1) 200 ml of sludge was collected. (2) When adding a metal salt, add the specified amount of the specified metal salt and stir at 250 rpm using a stirrer (2 blades).
Stirring was performed for 30 seconds. (3) A predetermined amount of a predetermined polymer and acid or alkali were added as the same solution, and stirred for 30 seconds at 250 rpm using a stirrer (two blades). (4) The produced floc was poured into a Buchner funnel lined with 100 mesh nylon cloth, and the liquid volume was measured after 10 seconds. (5) After 2 minutes, the sludge was sandwiched between a belt press dehydrator cloth (polyester, herringbone weave) and a sponge, and the water was compressed and dehydrated for 60 seconds at a pressure of 0.5 kg/ ^cm2 , and the water content of the dehydrated cake was measured. did. (6) The peelability of the cake from the cloth was investigated by washing the cloth with water and measuring the concentration of suspended solids in the washing solution. The results were as shown in Table 2. For comparison, the case where only A was added is also shown.

[Table] From the results shown in Table 2, the combined use of AH polymer and AA polymer in the presence of acid or alkali improves the gravity permeability and strippability of sludge, and reduces the water content of the dehydrated cake. I understand. Comparative Examples 3 to 7 When no alkali is added in Example 1 (Comparative Example 3), and when no acid salt is added in Example 2 (Comparative Example 4), DAM (CH ₃ Cl) and
Performance tests were conducted in the same manner as in the examples for cases in which DAM (CH ₃ Cl)/AAm copolymer was used alone (Comparative Examples 5 to 7). The results are shown in Table-3.

[Table] From Table 3, it can be seen that if an alkali or an alkaline salt or an acid or an acidic salt is not co-present, not only will the effect be inferior, but depending on the polymer, reactions will occur between the polymers and the effect will not be exhibited. moreover,
It can be seen that the present invention is much more effective than the case where a polymer containing an amino group or a quaternary ammonium salt is used alone. On the other hand, when A and B1 or B2 solutions are mixed, the solution becomes cloudy and the effect is extremely poor.

Claims (1)

[Scope of Claims] 1 Organic sludge, an acrylic acid hydrazide-based polymer compound, a polymer compound containing an amino group or a quaternary ammonium salt, and an acid or an acidic salt;
A method for treating sludge, comprising adding a solution containing a neutral salt and at least one selected from an alkali or an alkaline salt. 2 Acrylic acid hydrazide polymer compound has the general formula (In the formula, R represents H or _CH3 , A represents a monomer unit of acrylamide, methacrylamide, acrylic acid ester, methacrylic acid ester, and B represents acrylic acid or a salt thereof, methacrylic acid or a salt thereof, or the above-mentioned Claim 1 describes a compound that represents a monomer unit copolymerizable with A, and l, m, and n have the following relationship: 0 mol%<l≦100 mol% n+m+l=100 mol% sludge treatment method. 3. The polymer compound containing an amino group or a quaternary ammonium salt is an aminoalkyl acrylate,
The method for treating sludge according to claim 1 or 2, wherein the sludge treatment method is a compound selected from aminoalkyl methacrylate, aminoalkylacrylamide, aminoalkylmethacrylamide, or a quaternized product thereof.